Many lifting and positioning devices use a boom structure to lift and position a load. In some applications, the load platform needs to be kept level as the boom is raised and lowered. Some examples are a boom where the load is a person, or booms used to smoothly move and position an operating motion picture camera.
With a boom of fixed length, a common technique of maintaining a level load platform is through the use of an auxiliary fixed-length boom or arm, above or below the load-carrying boom, and parallel to the boom. This arrangement forms a parallelogram. If the attachment points for the boom and the second arm are collinear and perpendicular to the ground, and the boom and arm are equal lengths, then the attachment points at the other ends of the boom and arm will also remain collinear and perpendicular to the ground as the boom is raised and lowered. Any platform then attached at the end of the boom, perpendicular to the line formed by the attachment points of the boom and the arm, will thus be parallel to, and therefore level with, the ground at any height of the boom.
A shortcoming of these devices in the current art is their mechanical complexity, requiring time-consuming assembly and disassembly each time they are used. Another shortcoming is that, due to the nature of the boom designs in the current art, they often have a relatively long minimum fixed length dimension even when disassembled, making them difficult to transport. Still another shortcoming is that most if not all assembly methods entail the use of peripheral fasteners, clips, pins and other hardware that are easily lost over the courses of assembly, disassembly and transit.
In view of this, it would be desirable to develop a method or methods of constructing or fabricating a highly compactable camera crane.